Process for oxidizing asphalts



2,776,932 PnocEss FGR oxrnrzuvo ASPHALTS Harley F. Hardman, lLyndhurst, Ohio, assignor to The sgaggard Oil Qompany, Cleveland, Ohio, a corporation no No Drawing. Application May 6, 1953, Serial No. 353,448

4 Claims. (Cl. 196-74) This invention relates to an improved process for the treatment of asphalt stocks and more particularly to a process for producing asphalt having improved properties.

With the development of the extensive use of asphalt in bituminous type pavements, asphalts have been extensively investigated and a number of specifications have developed over the years. As more information has been accumulated, additional specifications have been added from time to time. However, penetration measurements, especially where made at different temperatures, are one of the most important characterizations, and penetration is invariably included in asphalt specifications.

Penetration is the consistency of a bituminous material, that is, the resistivity to deformation, and is expressed as the distance that a standard needle vertically penetrates a sample of the material under known conditions of loading, time and temperature. The test is standard in the industry. High penetrations indicate a softer asphalt.

Temperatures susceptibility is a calculated value and is a comparison of the consistency or hardness of the asphalt at some elevated temperature with the same property at a lower temperature. Numerically, it is the ratio of the penetration Value of the asphalt measured at a higher temperature to the penetration of the asphalt at a lower temperature. Several different higher temperatures and several different lower temperatures have been proposed as the best for comparison purposes. For purposes of the present disclosure, the two values are taken at 77 F. and 32 F, respectively. The temperature susceptibility is therefore defined herein as the ratio of the penetration at 77 F. divided by the penetration at 32 F. The lower this number the more desirable is the asphalt. This stems from the fact that the asphalt must meet a rigid 77 F. penetration, and if it has a low temperature susceptibility it does not become as hard or brittle at low temperatures, and there is less tendency for pavements made with such asphalts to deteriorate under the stress of use at low temperatures.

In order to understand more fully the significance of the above specification, it is believed desirable to explain briefiy the manner in which asphalt is made and the effect that the manufacturing procedures and the constitution of the asphalt may be expected to have upon the above-described specification.

When whole crude oil is distilled to remove all of the fractions that are volatile at atmospheric pressure up to a temperature below cracking, the undistilled remainder is commonly known as reduced crude. This reduced crude is then subjected to further distillation and fractionation under a vacuum, and various volatile fractions comprising lubricating oil fractions, waxes, and cylinder stocks are removed overhead. This operation is often carried out in a fractionating column known as a 2,776,932 Patented Jan. 8, 1957 pipe still, and the petroleum residuum is often referred to as pipe still bottoms. The composition of the pipe still bottoms will vary somewhat depending upon the source of the crude oil and the extent to which the volatile fractions were removed as overhead distillate. The pipe still bottoms as such are included with the term asphaltic stock as used herein and may be the final asphalt material or it may be further modified to form the final asphalt as explained herein.

Asphaltic stocks may be divided into two fractions, termed petrolenes and asphaltenes. The petrolenes constitute the fraction which is soluble in 50 volumes of normal pentane, and the asphaltenes comprise the fraction which is insoluble in normal pentane. These asphaltic stocks may be considered to be colloidal systems in which the asphaltenes constitute the dispersed phase and the petrolenes the dispersive phase. Since the petrolenes are generally liquids (although in some instances they have very high viscosities), and the asphaltenes are generally solids, the petrolenes may be regarded as plasticizers for the asphaltenes. The properties of the asphalt will be determined to some extent by the relative proportions of the asphaltenes and petrolenes. The higher the proportion of the latter, the softer will be the asphalt. It will be obvious in view of this explanation that the larger the amount of petrolene fraction that is distilled overhead in the pipe still fractionation, the smaller will be the amount of petrolenes remaining in the residuum. It is possible to operate the pipe still fractionation in such a way that no more than the requisite amount of petrolenes remains in the residuum to provide a straight-run asphalt of the desired penetration. For example, the pipe still may be operated under such conditions and for such a time that the residuum has a penetration of 70-80 at 77 F., a value commonly specified for asphalts.

In addition to the relative amounts of the petrolenes and asphaltenes, another factor that affects the properties of. the asphalt is the character of the asphaltene and petrolene fractions. The viscosity of the petrolene fraction may vary, and it will be obvious that the viscosity of this fraction will have an effect upon its plasticizing action and be instrumental in determination of the properties of the asphalt. Similarly the molecular weight of the asphaltenes can vary and will affect the properties of the asphalt.

As the distillation in thepipe still is continued, it will be obvious that the more volatile petrolenes, i. e., those having lower viscosities, will be distilled overhead. The petrolenes which remain are those of higher viscosities. Thus a straight-run asphalt will have petrolenes of a relatively higher viscosity.

The viscosity of the petrolenes is believed to be an important characteristic of asphalt due to the effect thereof on ductility, softening point, bleeding tendency, low temperature brittleness, oxidation resistance, and strip ping resistance. Petrolenes of low viscosity are particularly desirable in an asphalt to impart the last three properties. For this reason the straight-run asphalt is deficient in this respect.

Generally, however, the pipe still is not operated in a manner to produce a straight-run asphalt. Usually the residuum contains an amount of petrolenes in excess of thatto give an asphalt of the desired properties. Accordingly, it is common to heat the residuum alone or in the presence of a catalyst or accompanied by air blowing alone or in the presence of a catalyst to convert a portion of the petrolenes into asphaltenes.

The oxidation of the residuum, which is a commonly employed mode of operation, is usually efiected by blowing air through the residue at a temperature of about 400 to 500 F. at a rate of about 30 to 50 cubic feet per minute per ton of asphalt charge until the desired penetration is obtained. I l

In accordance. with the present invention, it has been found that the addition of certain catalysts to asphalts, before heating and before blowing if the asphalt is blown, produces a final asphalt product having an improved temperature susceptibility. The catalysts also result in hardening of the asphalt during the addition of the catalyst and before any oxidation or blowing is effected. With some stocks no oxidation-or blowing is necessary, and with others the oxidation time is shortened.

In accordance with'the invention, the asphalt derives its decrease inpenetration froman increase both in the molecular weight of the asphaltenes and in their concentration in the asphalt.- The'asphalts treated or prepared in accordance'with the invention possess a better temperature susceptibility than-do straight-run asphalts or asphalts prepared by heating or air blowing without our catalysts.

As will be seen from the data hereinafter, the use of the catalysts of the invention, whilepermitting the usual conversion of petrolenes to asphaltenes, causes a decrease inthc viscosity of the petrolenes. Apparently the heavier petrolenes are selectively converted to asphaltenes by the use of our catalysts with the result that the petrolene content has a lower viscosity with the consequent improvement in temperature susceptibility and low temperature brittleness. The use of the catalysts also causes an increase in. asphaltene molecular weight as well as asphaltene content. This tends to produce a more complex asphaltene system which imparts the desirable low temperaturesusceptibility. 1

The catalysts employed in the process of the invention are the heavymetalfluoborates. The heavy metals may be any of those having an atomic number in excess of 22 and having a pronounced metallic character as distinguished from arsenic, for example, which is a metal having certain properties of an acid. Among the above mentioned heavy metals which may be employed are: vanadium, chromium, manganese,:iron, cobalt,tnickel, copper, zinc, molybdenum, cadmium, tin, antimony, tungsten, silver, lead andbismuth.

The catalysts are added to the asphalt stocks in quaua tities of about 0.1 to by weight. and preferably 1 to 3% by weight of the asphalt stock. The temperature,

of the asphalt during incorporation of the catalyst is not critical, but the. asphalticstock is heated or heatedand blown with air until the requisite penetration is achieved,

depending on the specifications to .be met and the use to which the asphalt is to beput. Generally the temperature of the heating and/orheatingand blowing is 200 to 500 F. for a few minutes toseveral days. The lower the temperature, ,thelonger the time,.and vice versa. Neither is critical as long as the desired final penetration is met.

The invention will be further. illustrated by reference to the following specific examples. v

The results of a series of tests. are summarized. in Tables I and II below. In preparing these samples, two different pipe still bottoms fractions were heated to 200 to 300 F., after which the catalyst was added and the mixture was held at this temperature until any visible evidence of reaction disappeared. The penetration was then. measured to determine the amount of further oxidation necessary to obtain a satisfactory product. After measuring the penetration, the mixtures containing catalyst were heated to 425-450- F. and oxidized for a period sufficient to obtaina penetration of 70 to 80. Blank samples not containing the catalyst were also oxidized at 425 to 450 F. for the purpose of comparison. case 'the catalyzed asphalts had a lower temperature susceptibility than in the blank, i. e.,"the 100 F. pen. was lower and the 32 F.PCIL was higher, from which'it itwill be seen thatthe asphalt was stiffer at'the higher tempera-- ture and softer-at thelower-temperature than was the blank. Tables I and II illustrate the temperature sus- In each ceptibilitiesof the samples with various penetrations and show that the catalyzed asphalts were improved.

TABLE I Penetration Example Catalyst Soft. Pen. 77] Pt. Pen. 32 100 77 32 A None 212 10 23 125 3.05 1 c. 3% Cd fluoboratc. 202 78 31 132 2. 53 2 3% Fe iiuoborate. 127 03 27 152 2. 34 3% Ni fluo borate. 229 30 127 2.54 3% Pb fiuoborate. 227 78 31 132 2. 63 3% Zn fluoborate 128 74 27 129 2.

TABLE II Penetration Example Catalyst Soft. Pen. 77"] Pt. Pen. 32 77 32 B None 226 78 23 113 3. 39 6 3% S11 fluoborate 230 78 24 3.25

1 The sample prepared with stannous iluoborate did not require any oxidation. v D'atawasalso obtained showing the beneficial effects of the catalysts on the petrolene viscosity and the asphal' tene molecular-"weight of two different asphalt samples. These data are summarized in Table III.

TABLE III Effect of catalystszon molecular weight and asphalt composition variables Pctrolcnc, Asphaltene, Example Catalyst Vis. at M01. Wt.

N e 17, 600 610 3%-S11(BF4)2 12,200 2, 76!) None 5, 210 3, 350 3% Fe(BF4)z 3, 790 4 385 By comparison with the corresponding blank, it'is seen ceptibility which is in elfect a lowering of the point at which the asphalt becomes brittle is achieved by the presence' of'a petrolene fraction which has a lower viscosity at lower'temperatures. In other words, at low temperatures the petrolenes are sufficiently fluid to exert a plasticizing action on the asphaltenes.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof and the invention is to be restricted only in accordance with the appended claims.

I claimz 1. A method of treating an asphaltic stock comprising subjecting the stock to an elevated temperature in 'the presence ofv about 0.1 to 5.0% by weight of a fluoborate of a metal having aniatomic number in excess of 22 lam" 3. A method of treating pipe still bottoms comprising heating said material to about ZOO-300 F., adding about 1.0 to 3.0% by Weight of a fluoborate of a metal having an atomic number in excess of 22 and having a pronounced metallic character, heating the mixture to about 425450 F. and oxidizing said material to reduce the penetration to the desired value and to decrease the temperature susceptibility of the material.

4. A method of treating pipe still'bottoms comprising heating said material to about ZOO-300 F., adding about 1.0 to 3.0% by weight of a fluoborate of a metal having an atomic number in excess of 22 and having a pronounced metallic character, maintaining the mixture References Cited in the file of this patent UNITED STATES PATENTS 2,179,208 Burk et al Nov. 7, 1939 2,287,511 Burk et al. June 23, 1942 2,494,510 Hughes et al. Jan. 10, 1950 2,661,323 Kraft Dec. 1, 1953 

2. A METHOD OF TREATING AN ASPHALTIC STOCK COMPRISING HEATING AND OXIDIZING THE STOCK IN THE PRESENCE OF ABOUT 0.1 TO 5.0% BY WEIGHT OF A FLUOBORATE OF A METAL HAVING AN ATOMIC NUMBER IN EXCESS OF 22 AND HAVING A PRONOUNCED METALLIC CHARACTER TO DECREASE THE TEMPERATURE SUSCEPTIBILITY OF THE STOCK. 